topic Re: IFC import geometry unwieldy in Collaboration with other software

IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 06:41:38 GMT

When importing IFC (from Revit Structure) beams and columns generated from BREP (ie more complex than a flat extrusion) the geometry created either in Morph or Object format is of such a high polygon count that navigating the resultant model is impossible.

Does anyone know of a method to reduce the level of detail in the imported objects and profiles so that the intent (eg steel I beam) is maintained without the massive polygon count being generated?

Would also be useful to know of any methods for rationalising Morphs created from imported objects.

Re: IFC import geometry unwieldy

Laszlo Nagy — Wed, 15 May 2013 09:22:23 GMT

Are you using the Graphisoft IFC Revit Add-In when exporting from Revit? Does that make any difference?:

http://www.graphisoft.com/downloads/interoperability.html

Re: IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 09:24:56 GMT

We have tried both with and without the plugin. Grids etc work better with the plugin but the issue of geometry detail is still there.

Re: IFC import geometry unwieldy

Laszlo Nagy — Wed, 15 May 2013 09:33:40 GMT

Then you should report this issue with files to your local reseller for further investigation.

The Morph Tool has some commands for smoothing edges and faces but that may not give the result you are after. Other than that you can always select any unneeded edge and delete it (for example, if a planar surface is unnecessarily triangulated), but that may be drudgery if there are many such elements.

Please also note what I wrote in response to another IFC-related question, it may apply to your case as well:

http://archicad-talk.graphisoft.com/viewtopic.php?p=215277#215277

Re: IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 09:44:08 GMT

Thanks Laszlo,

We are already doing a version of that because of difficulty in getting the coordinate system coming out of the Revit IFCs.

Unfortunately the clean file that we are putting the Revit IFC into is barely navigable on its own and I'm too afraid to see what it does speed wise once I module it into our Teamwork project.

To give you an idea of the sizes we are talking about.
Teamwork file saved to a solo file as is = 140Mb
Solo file once all Sections, Elevations, Details and Layouts removed (ie model data only) = 5Mb
Clean ArchiCAD file with only the Revit IFC imported (no 2D data etc.) = 21Mb

If the structural model data alone is 4x the size of our architectural data we are going to have to start taking a lot of long coffee breaks while we wait for the sections to rebuild. (haven't had to do that since V11)

Re: IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 09:50:12 GMT

I don't mind so much that the more complex elements such as 20Ø rod cross braces come is as objects but when one I beam that is flat is recognised as a beam with a cross sections profile etc. and the one next to it is inclined at 3° and all of a sudden becomes a complex morph or library part with 1000's of triangulated faces.

In discussions with our engineer we think it has something to do with the angle the end of the member is cut at.

- In ArchiCAD a beam end is always vertical (unless you start doing SOE to it)
- In Revit a beam end is always perpendicular to the beam's axis and needs to be modified to give a vertical end if that is what the design requires.

It seems too much of an imposition to ask the engineer to design the beam ends in the project just to suit the limitations of IFC.

Re: IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 10:11:22 GMT

Just to clarify I've done the following snapshots of the same model in Solibri and ArchiCAD.

Re: IFC import geometry unwieldy

Matthew Johnson — Wed, 15 May 2013 10:20:31 GMT

And to give you an idea of the level of detail the morph bodies have.

No that's not a black material; that's the number of faces blurring to infinity. And at only half way through design development we already have over 1000 of these.

Re: IFC import geometry unwieldy

Anonymous — Wed, 15 May 2013 20:37:42 GMT

Any chance to post a single problematic beam as a revit file and resulting IFC file?

Re: IFC import geometry unwieldy

Laszlo Nagy — Thu, 16 May 2013 15:17:13 GMT

Does the exported IFC have a very high polygon count also in Solibri or only in ArchiCAD?
If the IFC already has a high polygon count than it has something to do with how it is exported from Revit.
If it has high polygon count only in ArchiCAD, then the ArchiCAD import of IFC is the culprit.

Re: IFC import geometry unwieldy

Laszlo Nagy — Thu, 16 May 2013 15:20:03 GMT

Matthew, you can either attach a ZIP file to a post (limited size) or give us a link to a file in Dropbox or something similar.

Re: IFC import geometry unwieldy

Matthew Johnson — Fri, 17 May 2013 00:41:17 GMT

Laszlo,

The attached screen capture shows the differences in polygon count between Solibri and ArchiCAD.

Some members, such as the I beam (running lower right to top left), seem to have a similar number of faces in both programs. Solibri identifies this as a beam.

Other members, such as the CHS struts with end plates, have far more polygons in ArchiCAD.

However, the model in Solibri is navigable with ease and shows no delays whereas navigating the model in ArchiCAD is very slow.

PS: Working on getting a Revit file from the engineer with just a couple of members in it for testing.

Re: IFC import geometry unwieldy

Laszlo Nagy — Fri, 17 May 2013 01:20:56 GMT

I don't have a solution so there is not much I can say, besides that you should report this through your local reseller.

Re: IFC import geometry unwieldy

Anonymous — Fri, 17 May 2013 04:44:37 GMT

Matthew,

I have had similar problems with Revit beams, columns and slabs that have cuts being imported as objects rather that beams and columns, with angled bracing being especially problematic.

My solution to the problem is to have a structural model (controlled by me) which I hotlink into the main project file. This file started as an imported file from revit and I went through the file and replaced the imported members that were blocks with beams and columns. When I now receive an updated structural model I reference this into the structural model and make required adjustments where the model differs from my model.

By doing this I have a model that is quick to navigate and section generation times are minimal.

Attached are a couple of views from my current project, I can navigate views in real time and sections and elevations only take a few seconds to regenerate.

Regards,
Scott

Re: IFC import geometry unwieldy

Anonymous — Fri, 17 May 2013 06:04:18 GMT

As Laszlo has indicated, if the revit export has exported a primitive object with lots of polygon faces, it's difficult to reverse engineer the intelligent object back out from it.

The Revit IFC exporter is openSource, so it might be possible to "improve" the export with a sample object to test with. I've been developing an IFC importer for Revit including IFC4 (http://geometrygym.blogspot.com/search/label/IFC) and I am also trying to get a chance to start working on an independent exporter too.

It should not be necessary to manually substitute objects each time a model is submitted, but certainly in this case (and Scott's by the sound) a higher quality IFC export would go a long way to help this.

Re: IFC import geometry unwieldy

Mats_Knutsson — Tue, 21 May 2013 11:40:53 GMT

We have another "problem" regarding the plan view of columns coming in (merge ifc) as objects (projection cut as A in attached image). To show the correct plan cut I change the "columnobjects" to morphs and then I can choose cut only (or with overhead), (B in attached image) as projection. Issues like this create the need for 2D dwg for the drawing production.
3D is fine